Abstract

Question

In patients with the irritable bowel syndrome (IBS), are smooth-muscle relaxants safe
and efficacious for global improvement of symptoms?

Data sources

Randomized controlled trials were identified by searching MEDLINE with the terms colonic
disease, functional, irritable bowel syndrome, and randomized trial; Current Contents; and bibliographies of relevant trials, meta-analyses, and reviews. Drug companies
were also contacted.

Study selection

Trials were selected if they were double-blind studies that compared muscle relaxants
with placebo, ≥ 51% of patients had IBS, the drugs studied had myorelaxant properties,
and ≥ 1 end point of global assessment of symptoms, abdominal pain, constipation,
or abdominal distention was included.

*Abbreviations defined in Glossary; RBI, NNT, and CI calculated from data in article.

Commentary

IBS represents a heterogeneous group of disorders presenting with similar clinical
symptoms. Altered motility is thought to be important in a subset of patients with
IBS, and this concept forms the foundation for the use of smooth-muscle relaxants.

3 recent meta-analyses, including the review by Poynard and colleagues, have evaluated
smooth-muscle relaxants for IBS (1, 2). Each found such agents better than placebo for global improvement and abdominal
pain. The latest, the review by Poynard and colleagues, differs from its predecessors
by excluding peppermint oil and dyciclomide bromide and including 6 additional randomized,
non-English-language trials. Although smooth-muscle relaxants appear superior to placebo,
Poynard and colleagues suggest that only approximately 50% of treated patients will
experience global improvement and only 40% will have an improvement in abdominal pain.
In addition, the results do not indicate which individuals are most likely to improve
with these agents. Perhaps most important, only 1 of the drugs included in this meta-analysis,
hyoscine, is available in the United States, and it showed the least benefit for global
improvement or abdominal pain over placebo.

If one accepts the issues noted above, it seems reasonable to conclude that as a class,
smooth-muscle relaxants can benefit a subset of patients with IBS. Unfortunately,
whether the results are generalizable to agents available to physicians in the United
States remains an open question.